The Federal Bureau of Investigation is looking at people with suspected links to al Qaeda who have shown an interest in mounting an attack on computer systems that control critical U.S. infrastructure, a senior official told Congress Tuesday.

While there is no evidence that terrorist groups have developed sophisticated cyber-attack capabilities, a lack of security protections in U.S. computer software increases the likelihood that terrorists could execute attacks in the future, the official warned.

If terrorists were to amass such capabilities, they would be wielded with "destructive and deadly intent," Steven Chabinsky, deputy assistant director of the FBI's Cyber Division, told the Senate Judiciary Committee Tuesday.